Mazy's Department Store has decided to stay open on a 24-hour basis. The store manager has divided the 24-hour day into six 4-hour periods and determined the following minimum personnel requirements for each period:
Time .......... Personnel Needed
Midnight–4:00 A.M. ........ 90
4:00–8:00 A.M. ......... 215
8:00–Noon .......... 250
Noon–4:00 P.M. .......... 65
4:00–8:00 P.M. ........ 300
8:00–Midnight ......... 125

Personnel must report for work at the beginning of one of these times and work 8 consecutive hours. The store manager wants to know the minimum number of employees to assign for each 4-hour segment to minimize the total number of employees.
a. Formulate a linear programming model for this problem.
b. Solve the model by using the computer.